The present invention relates to a vacuum actuated pickup instrument and a method of operating such an instrument and more particularly to such an instrument and method of operation adapted for use in handling relatively delicate or fragile objects.
Many different types of vacuum actuated pickup instruments have been provided in the prior art for handling a variety of objects. Some of these instruments are particularly contemplated for handling microelectronic wafers or chips of a type adapted for having printed circuitry or other components imposed thereupon. Such wafers or chips are relatively delicate or fragile and require a number of different operations to complete their construction.
With larger sizes of such chips and wafers being employed to increase capacity and productivity, the hazard of breakage is of even greater concern because of the greater value of the wafers or chips.
In many operations, automated equipment is employed for handling the wafers. However, even in such automated applications, many operations still require individual handling of the wafers and vacuum actuated instruments of the type provided by the present invention have been found particularly suitable for this purpose. Generally, such pickup instruments commonly include valve means for regulating the initiation and/or termination of vacuum conditions in a pickup head in order to selectively engage and release objects to be moved by the instrument.
One of the simplest valve mechanisms includes a flexible tube which can be pinched manually or by various valve means to terminate a vacuum condition. With such an instrument, the vacuum may again be initiated simply by releasing and allowing the flexible tube to expand and re-establish the vaccum.
Another type of valve arrangement includes a vent opening along a vacuum passage so that an operator may either close the vent with a finger to develop a vacuum or remove his finger to vent the passage and terminate vacuum conditions.
Somewhat more complex valve arrangements have also been employed in order to better adapt the instrument for use with delicate articles such as semi-conductor wafers of the type referred to above. For example, Lasto et al U.S. Pat. No. 3,071,402 discloses different embodiments of vacuum operated probe tools having either a slide type or push-button type valve for initiating and terminating vacuum conditions.
Furthermore, a number of patents have issued to one of the inventors of the present invention concerning similar vacuum actuated instruments. For example, U.S. Pat. No. 3,843,183 issued to Clifford L. Hutson discloses such an instrument including a slide valve movable to a first position to connect a nozzle with a vacuum source, a second position to disrupt communication between the nozzle and the vacuum source while maintaining the vacuum condition in the nozzle, and a third position to vent the nozzle.
U.S. Pat. No. 3,940,172 issued to Clifford L. Hutson et al also discloses a vacuum actuated instrument including a similar slide valve together with means for rotating a nozzle or tip of the instrument together with an object picked up by the instrument.
U.S. Pat. No. 4,050,729 also issued to Hutson dealt with similar vacuum actuated instruments while disclosing a triangular housing forming a preferred embodiment of a vacuum attachment nozzle or head for engaging objects such as semiconductor chips or wafers. Although the present invention does not deal with the particular configuration of the vacuum nozzle, it is noted that a vacuum attachment nozzle of the type disclosed in the above reference could also be employed with the instrument of the present invention.
In any event, a wide variety of such instruments is available in the prior art. However, because of the complexity and fragility of various objects requiring handling by such instruments, there has been found to remain a continuing need for improvement in such instruments and their capabilities. In addition, although the invention is described below particularly in connection with the handling of semi-conductor wafers of the type referred to above, it is noted that the vacuum actuated pickup instrument of the present invention may also be employed for handling objects of a wide variety. In particular, the instrument of the present invention is adapted for handling any objects, particularly small or fragile articles requiring substantial manipulation and having a surface adapted for engagement by a vacuum nozzle of the type employed with such instruments.